Converting lead acid to lithium batteries

[chet-ClassB]

I’m new to lithium batteries. I have a Chevy roadtrek 190 with lead acid batteries. My question is can I just replace the existing batteries with lithium without adding any other devices? Will the Tripplite inverter/charger work on them?
Being a novice with the electrical system any useful information would be appreciated.

 

[booster]

I’m new to lithium batteries. I have a Chevy roadtrek 190 with lead acid batteries. My question is can I just replace the existing batteries with lithium without adding any other devices? Will the Tripplite inverter/charger work on them?
Being a novice with the electrical system any useful information would be appreciated.

Some will depend on the year of the Roadtrek as the wiring changed over time. The Tripplite is not particularly good for lithium so it really should be changed. Most likely a battery to battery charger for the alternator charging so you don't wreck the alternator.

How much battery bank you plan on using is important to know, as well as camping style and if you want to run the microwave or air conditioning on batteries. Even where you live and store can make a difference.

There are quite a few lithium swaps, including our 07 190P one, on this forum so probably would want to read a bunch of the discussions on how they were done.

No matter what the sellers tell you, IMO lithium swaps are never just drop in.

 

[chet-ClassB]

Thanks for your reply Booster. I have some homework to do since it doesn’t sound like a plug and play situation. I only have one chassis alternator and a two 100AH battery bank which is original setup from manufacturer; it was purchased used. I need to look into those previous posts on how to. The RV sits outside in the winter but will not be used. Thanks again.

 

[booster]

Thanks for your reply Booster. I have some homework to do since it doesn’t sound like a plug and play situation. I only have one chassis alternator and a two 100AH battery bank which is original setup from manufacturer; it was purchased used. I need to look into those previous posts on how to. The RV sits outside in the winter but will not be used. Thanks again.

You may or may not be the same as our 07 wiring as there was a change right around then that changed a bunch of the cable sizes in particular. We had the same two batteries one on each side of the R/H rear wheelwell.

A lithium system that sits outside in the winter will likely need to be able to be heated to protect the batteries depending on what coldest temps it will see. Or the batteries removed and stored indoors.

 

[phantomjock]

Chet, I missed the year group or base model - Chevy, Dodge, etc. of your 190. I assume a Chevy 3500?

Cheers - Jim

 

[chet-ClassB]

Yes, it’s a 3500 Chevy 190 -2008 model

 

[chet-ClassB]

You may or may not be the same as our 07 wiring as there was a change right around then that changed a bunch of the cable sizes in particular. We had the same two batteries one on each side of the R/H rear wheelwell.

A lithium system that sits outside in the winter will likely need to be able to be heated to protect the batteries depending on what coldest temps it will see. Or the batteries removed and stored indoors.

Booster
Do you have any recommendations on replacing the existing Tripplite? You said it’s not a good fit for lithium.

 

[booster]

Others may have different but any that have settable charge voltage and full shutoff once charged. Not a lot have that and they can get expensive.

If you don't need a large charger, like you probably won't, a Renogy isn't a bad choice as long as is one of them that does full shutoff. I don't all models of Renogy do full shut off.

Remember that you will also need a battery to battery charger for charging off the engine.

It is always a good idea to start with how you would handle the tougher to do issues like battery heat or removal in the winter. Battery heaters that run off the battery are only for short time use, not storage unless shore power powered. Stuff like this can help determine which batteries and equipment you will need.

 

[Winston-ClassB]

Booster: "any that have settable charge voltage and full shutoff once charged."

Booster, why do you want it to shutoff when your target voltage/SoC is reached? The beauty of a constant voltage charge source is that the charger (power supply) serves as the source of power for your loads rather than the batteries. We see no reason to constantly cycle ones batteries when on shore power.

So we would recommend any charger in which you can set a "Constant Voltage" output.

 

[booster]

Booster: "any that have settable charge voltage and full shutoff once charged."

Booster, why do you want it to shutoff when your target voltage/SoC is reached? The beauty of a constant voltage charge source is that the charger (power supply) serves as the source of power for your loads rather than the batteries. We see no reason to constantly cycle ones batteries when on shore power.

So we would recommend any charger in which you can set a "Constant Voltage" output.

Hi Winston, good question.

I am basing it on the research papers and testing I have seen into failure analysis for the LifePo4 batteries and also that quite a few commercially available lithium chargers have switched to full cutoff charge profiles.

What they found was that holding any voltage potential on the batteries built up surplus ions on the cathodes(?) and those ions caused cathode plating in the form of dendrites that would build until they poked though the insulating layers and shorted the cell. It appears that it happens at any held voltage but plating worsens the higher the voltage is.

The recommendation to not hold the batteries at full state voltage of 14.4-14.6v has been around for a long time, but now it appears to be expanding to any voltage, at least that people charge at.

The same theory of ion buildup is being applied to the problems seen in high rate charging which generates a larger voltage potential on the poles, and the bigger that potential the worse the dendrite formation. The current pretty common .2C to .4C with .2 preferred is a huge reduction from what we saw just a few years ago.

We are still experimenting with our charging parameters, but it looks now that what we are currently doing is not too bad. We shoot for 35-85% SOC all the time.

Major charging is done with the alternator at 120 amps, .2C. It stops at around 85% but the regulator can't control exactly.

When the SOC gets down to about 50% we turn on the solar panels which, on average, can produce slightly higher amp hours that our daily use so SOC normally very slowly climbs over time. Probably 3/4 of our trips are more we haven't even needed to use the alternator again over 2-3 trips. If we do go backwards we just run the alternator charging for a trip to a trialhead, store, or dump station. So we are very slowly doing midrange very low amperage (max about 14 amps) daily with the solar most of the time now.

 

[Winston-ClassB]

You've probably heard our argument before . . . that being, if we take a lithium battery that's resting at, say, 90% SoC with a corresponding terminal voltage - - in our case, approximately 13.36 volts - - and connect that battery to a 13.36 volt power supply, nothing will happen. No current will enter the battery, no current will leave the battery. In short, the battery won't know that a power supply has been connected. So, we're perplexed how the battery can build up excess ions without any current flow.

And then there's the question, or trade-off, how much are we shortening the life of the battery by unnecessarily cycling it? Maybe, rather than finding a charger that will turn-off after charge is reached, we should disengage the batteries?

 

[booster]

You've probably heard our argument before . . . that being, if we take a lithium battery that's resting at, say, 90% SoC with a corresponding terminal voltage - - in our case, approximately 13.36 volts - - and connect that battery to a 13.36 volt power supply, nothing will happen. No current will enter the battery, no current will leave the battery. In short, the battery won't know that a power supply has been connected. So, we're perplexed how the battery can build up excess ions without any current flow.

And then there's the question, or trade-off, how much are we shortening the life of the battery by unnecessarily cycling it? Maybe, rather than finding a charger that will turn-off after charge is reached, we should disengage the batteries?

From what I have seen on our batteries it would take a very long time to get to zero amps, although we wouldn't be able to tell exactly due to the internal BMS draw.

I guess the question I would have in real life is what happens when you put a load on the system and the voltage drops before the power supply can react or if the load exceeds it's capacity? Perhaps you are talking about when the batteries are stored, though so no in or out except for a slight parasitic internally.

I think and interesting experiment would be to disconnect the power supply for a set amount of time, maybe 72 hours our even a week or two. The put it back on and see if there is any current taken. If there is current taken, it would seem to indicate that there is a very small current going in all the time to cover the parasitic loss when the voltage is applied all the time.

I am counting on the studies that showed that low rate, midrange, charging gave recharge cycle life in the 10s of thousands cycles when compared to particular 20% to 100% (14.4v) cycle life of 2-3000 cycles.

 

[Winston-ClassB]

As to charge rate, GBS (9 years ago) spec'd these batteries for 3C . . . 1,500 amperes for our 500ah pack. However, that number is unrealistic with 250 amps being our highest charge rate with 150 amps or lower being the typical.

Most of our capacity tests have been conducted by discharging the battery a known amount, often in 10% (50ah) increments, then, completely removing all connections to the battery. We found that it takes about 5 hours for the battery voltage to stabilize (to within the 0.01 volt resolution of our Fluke) . . . but we typically allow 10 - 15 hours of resting before we take an official reading. Thus, the 90% SoC reading of 13.36 volts was the voltage at 90% SoC after 15 hours of resting. Yes, there will eventually be additional changes due to self-discharge, but these are relatively triffling. What we've chosen to do is "match" what the battery is telling us. So, if we desire to maintain our system at a 90% SoC, we set our power supply to 13.36 volts and connect it to the battery. If no loads are connected, nothing happens - - no current flows. In real life, of course, there are always loads. We assume that the power supply is supplying the current required of these loads but in reality there probably is some sharing. But when all is said and done, if the battery has contributed to the load, the power supply will seek to restore the battery to the 13.36 volt level. In normal day-to-day operation, the system voltage remains constant (except under very large loads) and we think it safe to conclude that the power supply is sourcing the current to the loads. As measured by our BMS, currents are too small to read accurately with the system seemingly randomly, often in quick succession jumping between "CHARGING" and "DISCHARGING" indications - - that suggests we're sitting so close to zero battery current that the sensing circuitry can't decide whether to report a Charge or Discharge condition.

Maybe in view of the fact that our batteries are down to 75% capacity with a noticeably higher internal resistance - - after 8 years - - suggests that they have received too many of those poisoned ions . . . but the simplicity of operation, the seemlessness of operation where we never - - while on shore power - - have to monitor SoC and periodically intervene to recharge our batteries is a benefit arguably worth the risk of shortened battery life.

 

[booster]

Interesting that what we are talking about is only on shore power. At least in our world as we see and do it now, shore power doesn't really exist when we are traveling unless we need AC on horrible hot days, especially after a long hot drive. A couple of years ago on our yearly spring Custer trip, on the way home the first day of two driving to get home we drove in 100*+ temps for nearly 5 hours on the freeway at 70+mph. We got to the campsite at about 5pm, opened the hood turned on all the fans to cool the inside a little while underbody cooled a little and we sat outside under a shady tree. That night we did use AC and shore power as the was still 90* and the van was still hot. Other than that never plugged in, and when I did I just shut off the charger on the control panel.

Over the winter I can have it plugged in and have the Magnum take care of everything. It is set for fixed voltage and set time absorption two stage with "silent" float that means it goes off but comes bag on a set voltage. It cycles in the range of 50-80% at 40 amp charge rate. It will run two to four times a winter as I leave the van 12v system on to maintain the battery monitor SOC information which means we have about a .4 amp discharge rate. It is inside so never sees colder than about 45*.

I was truly surprised when you mentioned a while ago about your batteries were nearing the 80% remaining capacity norm for saying at or near end of life. I expected a well thought out and operated system like yours would last much longer. It seems that most even decently setup systems start to have problems in the 7-8 year range, so all the "save the battery" things may be mostly moot in the real world. With the price of lithium getting so much lower that also makes care and feeding convenient rather than nannied sound a lot more desirable. Turning on the solar to take care of much/all of our daily use recovery is really trouble free for us compared to watching for needing to turn on the alternator charging when driving. The solar is not capable of putting in enough current to overcharge the batteries unless it was perfect some for several weeks so set and forget for the most part, and never plug in even if we have shore power available.

Have you decided what you are going to do to replace the bank yet? I think you were leaning into just replacing the cells, and that certainly would be what I would do.

 

[Winston-ClassB]

Last question, first. No. We have been attempting to negotiate directly with GBS and with EVLithium. Do you know anything about EVLithium? The difficulty is, we don't think this is a good time to be buying anything from China - - so we may delay as the need is not critical (yet).

We mispoke by singling-out shore power. Our comments would apply to any charge source, indeed, we program our solar panels the same way - - to the desired target voltage for the chosen SoC. We treat our third charging source - - the second alternator - - differently. The purpose/use of the 2nd alternator is to quickly recharge the batteries. With that goal, we have selected a compromise voltage of 13.8 volts that 'compromises' between charge rate and alternator temperature. At that voltage we can run the 2nd alternator without the vehicle moving, for a reasonable amount of time (depending an ambient temperature) while maintaining an initial charge rate of 150-175 amperes.

The Magnum charger is, of course, automatically turned-off when there's no shore power. With shore power connected, it's always on (it's Magnums CC/CV mode) - - set to our target SoC voltage. For extended periods of disuse, we dial the SoC (Magnum Constant Voltage) down to 50%, but the Magnum is always "on". We don't cycle in a range as you are doing.

 

[engnrsrule]

Hey Chet-ClassB

Check out my thread where I upgraded the electrical on a 2006 RT, also equipped with a Tripplite Inverter/Charger. This system has been working great. I also added about 250w of Solar, but that's a different thread.

Thread: Roadtrek RS Adventurous Inverter Upgrade

Cliff Notes:

The Tripplite 750w inverter in 2006 was a modified sine wave inverter. New electronics require pure sine wave inverters, so this started as a inverter upgrade to a 1500w pure sine wave.

Initially intended to retain the TL in charge only mode, but went to a better 4 stage and higher capacity charger. This new charger was said to be compatible with Lithium batteries. For now I am still running lead acid, 2 6v in series for 235 ah.

The 2006 had only 2 outlets in the RT powered by the inverter. By removing the TL I had to redirect power source for these back to the main panel. Other outlets only had power if on shore tie or generator. I modified to have the new inverter feed the entire 120v panel.

A mechanism must be incorporated so that the inverter CANNOT power the battery charger. I managed this with a second Auto Bus Transfer Switch.

Much discussion about Neutral-Ground Bonding. Need to grasp this issue working with multiple possible 120v power sources.

Booster provided MAJOR advice/assistance throughout. Probably the smartest RV electrical guy I know.

 

[SQUASHMIRE]

Others may have different but any that have settable charge voltage and full shutoff once charged. Not a lot have that and they can get expensive.

If you don't need a large charger, like you probably won't, a Renogy isn't a bad choice as long as is one of them that does full shutoff. I don't all models of Renogy do full shut off.

Remember that you will also need a battery to battery charger for charging off the engine.

It is always a good idea to start with how you would handle the tougher to do issues like battery heat or removal in the winter. Battery heaters that run off the battery are only for short time use, not storage unless shore power powered. Stuff like this can help determine which batteries and equipment you will need.

How did you decide that you would 'need' a dc to dc charger? I just put in lithium in a truck camper and don't have that, but the alternator delivers 5-7 amps through the 7-wire pigtail. And that seems fine when driving every day. I do have plenty of excess capacity in my alternator. What am i missing?

 

[booster]

How did you decide that you would 'need' a dc to dc charger? I just put in lithium in a truck camper and don't have that, but the alternator delivers 5-7 amps through the 7-wire pigtail. And that seems fine when driving every day. I do have plenty of excess capacity in my alternator. What am i missing?

If you have lithium battery and are charging with an alternator and only get 5-7 amps charge current, you either have very low charge voltage at the battery or/and major voltage drop from undersized wiring or bad connections.

I would recommend finding out why you are charging so slowly. If it is resistance in wires or bad connections you can quickly get into a fire hazard situation from overheated areas.

 

[SQUASHMIRE]

I think the reason for charge current from the alternator of only 5-7 amps is the lithium batteries are near full SOC. So, again, why do I need a dc-dc charger?

 

[RT-NY]

I don't use a dc-dc charger. My 100ah lifepo4 battery draws on average about 20amps from the alternator when charging. I am guessing that it is limited by the voltage drop from my battery isolator. But, I do keep a careful eye on it -- I kept the old agm battery in place when I added the lithium and have a manual switch between them, so I use to that to avoid charging the lithium from the alternator when necessary. I usually only charge from the alternator when I am going to be on the highway for a while.

A dc-dc charger would be safer, but I chose the simplest, easiest, and cheapest solution. Not quite "drop in" but close. And it works fine in practice -- I can boondock indefinitely with the lithium (and my generator) which I could not do with the agm.