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Old 01-11-2019, 03:38 PM   #41
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Yes, Mr. booster stated that I had trained myself like a puppy or something like that. Hey, I'm a full grown dog now, just took some time.Bud

IIRC the comment was something like the owners of new puppies that are being housebroken seem to be trained to put the pup out based on signals from the pup, so the owners get trained by the pup before the pup gets trained eventually.


So in this case, Bud's power system would be the pup giving signals and he would be the "owner in training". So I guess we would have to say I called his van a pup (no an old dog)?
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Old 01-11-2019, 04:05 PM   #42
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My understanding is that the reason for the "rest" period is simply that it provides a standard condition for measurement.
Hi Avanti, yes I think the true charge condition of a battery is resting voltage as that is its baseline, standard condition for measurement as you well stated.

Relying on voltage readings while in service is a reasonable system health indicator if you keep in mind what loads are in play at the time. I did it that way for years.

Now on my new lithium build, I prefer to monitor how many amperes are left in storage. A flat lithium voltage curve is not helpful in determining remaining battery ampere level.

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Old 01-11-2019, 04:38 PM   #43
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Our concept of 'resting voltage' is to determine what the voltage is AFTER these temporary sagging/recovery effects have 'run their course'. We find that the pack voltage will 'recover' slowly for several hours after each discharge segment. We consider the recovery to have 'run its course' when the pack voltage no longer increases - - generally we require several hours of 'no (voltage) change' before taking our reading. To be on the safe side, we've been letting our pack 'rest' for 10 hours after each discharge segment..
10 hours is a long time to wait if your are using the van in any meaningful way. None the less, it's good to know how you define this measure.

For me, I'll start recording my 'resting voltage' when I get back from camping trips and try to calibrate it against measurements I take right at the end of the trip (before the batteries can settle). My home made battery management tools only work with real time measurements...
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Old 01-11-2019, 04:47 PM   #44
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Now on my new lithium build, I prefer to monitor how many amperes are left in storage. A flat lithium voltage curve is not helpful in determining remaining battery ampere level.

Santiago
Please share your setup and observations once you get some data. I'm also measuring the amps in and amps out on my battery and have determined that something just isn't adding up.

For example, I reset the 'Charge Meter' to zero when I was about at 45% SOC. I charged to about 85% with a positive 85Ah on the meter. While camping for several nights I observed consumption around 25 to 45Ah. However on each charge cycle, the total on the Charge Meter would creep up. Like 94 or so after the first cycle. Then 105 on the next, etc. Right now, after 'resting' for a few days and after I used a fair amount of power to dump the tank and clean up I'm seeing 125Ah on the meter (screen shot attached). This can't be right; it should be 85Ah or less.

In the mean time, I'm following the battery specs and ensuring that I don't charge any cell over 3.6V nor do I allow a cell to discharge below 3.2V as measured for at least 3 seconds at any time during charging or discharging. Seems to be better safe than sorry..
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Old 01-11-2019, 06:06 PM   #45
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Please share your setup and observations once you get some data. I'm also measuring the amps in and amps out on my battery and have determined that something just isn't adding up.
Hi Kite Rider, yes I will share all the electrical I manage to cobble together when I have something to show.

On your monitor, are any negative returns bypassing the monitor's shunt ?

As I mentioned earlier, my scheme is exactly the same as another Promaster member (tgregg) is using successfully to manage his lithium bank. His monitor is the Victron 700 series with built in high and low contacts that turns charging on and off. I believe I know another Promaster DIY fellow that used same charging control scheme when charging his lithium from the chassis battery using the Victron monitor and as far as I know is happy with it.

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Old 01-11-2019, 06:31 PM   #46
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What I have read, but have no idea if it is gospel, is that the rest time in lead acid batteries is needed to allow the electron migration through the battery to finish and be uniform. It was referred to as surface charge in reverse, as it gives a similar false actual voltage, but in the opposite direction compared to surface charge. I don't know it it also applies to lithium, and if it does, would it take as long with their high charge and discharge rates?

.........................
I have BlueSea OLED mini voltmeter on the galley front panel. I found it to be a highly visible reference point, it uses 10 mA so it is on all the time. Certainly, doesn’t provide the same information as SOC computed from Ah tally.

I think that during charging electrochemical capacitive double layers at anode and cathode are formed with some level of impedance. A double layer a layer with ion concentration gradient from low at the electrode to high towards the electrolyte. After charging this double layer goes away (ion diffusion) reflected in a lower resting voltage.
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Old 01-12-2019, 02:19 PM   #47
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10 hours is a long time to wait if your are using the van in any meaningful way. None the less, it's good to know how you define this measure.
Don't misunderstand . . . we're not proposing using voltage with, or without, long waiting periods as a real-time method for monitoring and controlling our house battery. We use a coulomb/amp-hour 'counting' meter as many on this forum do for real-time monitoring.

We undertook these tests, in part, as a curiosity, to establish a datum, and to measure overall pack capacity. We also wanted - - as most SOC vs Voltage graphs depict a family of curves under varying loads - - to create a graph of SOC vs No Load/Resting Voltage.

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As I mentioned earlier, my scheme is exactly the same as another Promaster member (tgregg) is using successfully to manage his lithium bank. His monitor is the Victron 700 series with built in high and low contacts that turns charging on and off.
In view of the continuing 'discussion' about 'drop-in' lithium replacements, it is noteworthy that TGregg's approach was motivated by the belief (one we support) that lithiums should not be subjected to the continuous 'high voltage' of a standard alternator programmed to maintain AGM batteries fully charged. We think others desirous of charging a lithium house battery from a standard Class B alternator should implement TGregg's system for terminating charging at a predetermined (non-100%) SOC level.

Fortunately with our 2nd alternator (with its external Balmar regulator) we are able to 'lithium program' the alternator (as we also do with our solar and shore power chargers) and don't have to rely on a BMS-generated SOC signal to interrupt charging.
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Old 01-12-2019, 02:56 PM   #48
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Fortunately with our 2nd alternator (with its external Balmar regulator) we are able to 'lithium program' the alternator (as we also do with our solar and shore power chargers) and don't have to rely on a BMS-generated SOC signal to interrupt charging.

How do you have the Balmar set for the DIY "lithium" program? Looking at the Balmar literature, I have never seen a way to do full shut off or to use anything other than changing voltages and max times, and then relying on the algorithms to do their thing. Are you just setting charge and float to your ending voltage?
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Old 01-14-2019, 06:43 PM   #49
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How do you have the Balmar set for the DIY "lithium" program?
The Balmar, like most smart chargers, is set up on the assumption that the user wants a Bulk, Absorption, Float charging profile. We don't. We program the Balmar like we do our other chargers (the Magnum 2812 and the MidNite Solar Classic) for Constant Voltage operation. But unlike these two other sources, we don't regularly use the 2nd alternator and, when we do use it, we use it manually in the sense that we manually turn it on and, thereafter, monitor the battery's SOC and, again manually, turn it off when our SOC target is reached. One other significant difference is, we use the 2nd alternator to fast charge our lithium pack so, to that end, we have chosen a much higher Constant Voltage (13.8 volts) than we ordinarily run with our other chargers (13.4 volts). We're contemplating raising the 2nd alternator to 13.9 volts hopefully increasing the charge rate without exceeding temperature limits.

One other significant parameter to note respecting the Balmar, we have set the Bulk Mode duration to 8 hours. As we never drive that long, anytime we use the 2nd alternator it is in the Bulk Mode at 13.8 volts.
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Old 01-14-2019, 07:08 PM   #50
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The Balmar, like most smart chargers, is set up on the assumption that the user wants a Bulk, Absorption, Float charging profile. We don't. We program the Balmar like we do our other chargers (the Magnum 2812 and the MidNite Solar Classic) for Constant Voltage operation. But unlike these two other sources, we don't regularly use the 2nd alternator and, when we do use it, we use it manually in the sense that we manually turn it on and, thereafter, monitor the battery's SOC and, again manually, turn it off when our SOC target is reached. One other significant difference is, we use the 2nd alternator to fast charge our lithium pack so, to that end, we have chosen a much higher Constant Voltage (13.8 volts) than we ordinarily run with our other chargers (13.4 volts). We're contemplating raising the 2nd alternator to 13.9 volts hopefully increasing the charge rate without exceeding temperature limits.

One other significant parameter to note respecting the Balmar, we have set the Bulk Mode duration to 8 hours. As we never drive that long, anytime we use the 2nd alternator it is in the Bulk Mode at 13.8 volts.



I kind of guessed it would be something like that if you didn't do the attempt at automatic function, which the Balmar isn't all that good for.


We have AGM on Ample Power regulator that runs both alternators, so don't disconnect completely. I can force to float, though, and do that manually, much as you do, as the Ample Power also sucks at automatic. I read SOC indirectly by a dash mounted ammeter to see battery charging amps. I take it to float when we hit a point that the solar will handle to finish off the charge automatically.
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