Help us decide

[W9TR]

Originally Posted by Bud

That seems surprising. How did you determine that?

If Thor is using their own inverter/charger, it appears to be 35 charging amps whether it is a 1, 2 or 3000 watt inverter/charger. If so, I would not use a LOUD onan to charge, rather the Promaster, Transit or whatever van. It appears that the microwave is covered so that leaves THE reason for a Loud onan or a quiet generator is the classic application, a/c.

Most wonderful to have no issues with a new B, always good to hear. Thanks for posting.

Bud

Bud - I determined it very unscientifically by running the converter for 30 minutes and looking at the battery voltage and doing the same for the engine driven alternator. They both raised the voltage from 11.5 to 12.0 volts in that time.

I need to install a shunt to see what’s really going on. The converter is a WFCO rated 35A @ 13.6V . Not sure what the Promaster alternator puts out at idle.

Tom

[Bud]

Originally Posted by W9TR

Bud - I determined it very unscientifically by running the converter for 30 minutes and looking at the battery voltage and doing the same for the engine driven alternator. They both raised the voltage from 11.5 to 12.0 volts in that time.

I need to install a shunt to see what’s really going on. The converter is a WFCO rated 35A @ 13.6V . Not sure what the Promaster alternator puts out at idle.

Tom

Hopefully which would usually be the case, a 35 amp charger with shore power or much worse yet a LOUD onan can't complete with the van's (any?) alternator.

Nice rv you have there.

[W9TR]

The 280 HP Promaster engine is way quieter than the 5 HP Onan Generator. I’m not sure I’ll use the generator very often. The only appliance I can’t run on the battery is the microwave. So far we think this RV will serve us well.

[jakegw2]

On my Promaster with a 220A alternator I get between 70 and 120 amps flowing from the alternator to the battery bank at idle. I presume it fluctuates based on loads from the chassis. It usually starts out on the high side and then drops and settles in the 70A-85A range after a while.

[W9TR]

Very helpful info. If I can get this kind of charge rate out of the main alternator my conversion to all battery will be easy. Meanwhile I'm going to buy and install a better muffler for the genset, although most of the racket seems to be just mechanical noise.
Tom

[rowiebowie]

A resonator will quiet the generator a little bit. But the biggest improvement is a lower and more pleasing exhaust note. I believe you are right that some of the exhaust sound is metallic-like valve clatter. The resonator will mute this more that actual decibels.

All my observations above are subjective. I didn't take any sound measurements before or after. I consider it worth it, just don't expect miracles.

[jakegw2]

Easier than most seem to think.

I pulled out my 2 AGM 105A group 27 batteries and replaced them with two 100A Battleborn LiPo batteries last weekend. When I talked to Battleborn they told me I would need some way to protect my alternator and prevent the batteries from getting over 50A of charge each. I was not sure this was necessary, but I went ahead and installed a switch by the drivers seat that lets me manually disconnect the battery isolator solenoid whenever I want.

Once they were in I started doing testing. So far I have seen no evidence that just leaving the Promaster alternator connected in any way exceeds the specifications on the batteries in a problematic way.

- As stated above, when the van is first started and the batteries are not full they absorb about 120A (60A each - BB stated they can take up to 100A charge but it shortens the life, while at 50A they will last their full rated lifetime). This sounds bad, but it really only lasts a few minutes before settling down to a lower charge rate of around 70-85A (35-43A each).

- When the batteries approach 95-99% charge (still need more testing to narrow down this value) the charge provided by the alternator decreases to a trickle of 0.2A. So it doesn't look like the alternator alone will get to 100%. Not a problem, my solar charger tops off the remaining ~10A without any problem (I have 340W of solar, so this is < 30 min in the sun, longer on a cloudy day). It also means that I don't really need a DC-DC charger - what a waste of a few hundred dollars to get that extra few percent from the alternator. Additionally, I don't seem to need it to limit the charge current. If I put in a 60A DC-DC I would only be limiting the current by about 25A. With only 200A of storage the alternator should be fine with the current set up. Perhaps if I had a 400A bank this might be a bit much to run the alternator at full output for 5 hours straight, but I could still space out the charging by just pressing my manual disconnect button and leaving it off for 20m or so every hour while driving to cool it down until the bank was full.

When I was researching this it seemed like everyone planned for fairly complicated setups with DC-DC chargers, special isolation solenoids that automatically connect and disconnect the alternator connection on a schedule to prevent overheating, etc. From my testing it really doesn't look like any of this is necessary with the Promaster alternator (unless you are installing a larger bank).

[rowiebowie]

Originally Posted by jakegw2

Easier than most seem to think.

I pulled out my 2 AGM 105A group 27 batteries and replaced them with two 100A Battleborn LiPo batteries last weekend. When I talked to Battleborn they told me I would need some way to protect my alternator and prevent the batteries from getting over 50A of charge each. I was not sure this was necessary, but I went ahead and installed a switch by the drivers seat that lets me manually disconnect the battery isolator solenoid whenever I want.

Once they were in I started doing testing. So far I have seen no evidence that just leaving the Promaster alternator connected in any way exceeds the specifications on the batteries in a problematic way.

- As stated above, when the van is first started and the batteries are not full they absorb about 120A (60A each - BB stated they can take up to 100A charge but it shortens the life, while at 50A they will last their full rated lifetime). This sounds bad, but it really only lasts a few minutes before settling down to a lower charge rate of around 70-85A (35-43A each).

- When the batteries approach 95-99% charge (still need more testing to narrow down this value) the charge provided by the alternator decreases to a trickle of 0.2A. So it doesn't look like the alternator alone will get to 100%. Not a problem, my solar charger tops off the remaining ~10A without any problem (I have 340W of solar, so this is < 30 min in the sun, longer on a cloudy day). It also means that I don't really need a DC-DC charger - what a waste of a few hundred dollars to get that extra few percent from the alternator. Additionally, I don't seem to need it to limit the charge current. If I put in a 60A DC-DC I would only be limiting the current by about 25A. With only 200A of storage the alternator should be fine with the current set up. Perhaps if I had a 400A bank this might be a bit much to run the alternator at full output for 5 hours straight, but I could still space out the charging by just pressing my manual disconnect button and leaving it off for 20m or so every hour while driving to cool it down until the bank was full.

When I was researching this it seemed like everyone planned for fairly complicated setups with DC-DC chargers, special isolation solenoids that automatically connect and disconnect the alternator connection on a schedule to prevent overheating, etc. From my testing it really doesn't look like any of this is necessary with the Promaster alternator (unless you are installing a larger bank).

A DC to DC charger between your engine alternator and lithium battery bank is not costly or complicated to install. It protects your alternator from burning out from delivering more amps than it is designed to handle. Your battleborns will get a proper lithium charge profile as well to make them last longer.

I wouldn't risk damage to either my expensive batteries or my alternator which could potentially leave you stranded. A DC-DC charger was only about a $160 addition to my Renogy lithium upgrade. Cheap insurance and you don't have to watch it or worry about it.