Balancing Battery Charger, Solar Controller, and Trimetric

unyalli
unyalli Solar Expert Posts: 121 ✭✭
in Off Grid Solar & Battery Systems #1
Don't believe I've seen this discussed. Thinking about disconnecting my WFCO 8955 powercenter's converter/charger and installing a Progressive Dynamics PD 9245C much closer to the batteries for charging on shore power. The WFCO is 15 to 20 foot of 10 gauge wire away from the GC2's. I believe I would need to monitor a full charge cycle of the PD's charge wizard with the Trimetric then set P1, P2, and P3 accordingly then set the solar controller voltages to match. Sound about right? Anyone done this?

Jeff
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Balancing Battery Charger, Solar Controller, and Trimetric

    I am not quite sure I understand... But starting with the basics, a 45 amp charger on 10 AWG circuit 20 feet (one way or round trip?) away (use 20' one way for worst case). Using a generic voltage calculator, the calculated drop is 2.2 volts.

    If you want fast/accurate charging for a 12 volt battery bank--Any 'error' in measured battery voltage that exceeds ~0.1 volts (for a 12 volt battery bank--and I would suggest a design drop of 0.05 volt drop would be even better) will slow charging (less current flow) and be less able to support DC loads when on shore power.

    For example say it has 13.6 volts float. And you put a 45 amp DC load (~500 watts) on your DC system. The voltage at the battery would have to drop to (13.6-2.2 volts=) 11.4 volts at the battery bank to have the DC converter (aka battery charger) support 100% of the load.

    So, moving the converter closer to the battery bank, using heavy gauge cables, etc. is all going to be helpful here.

    The Trimetric should be wired to the battery bus (as little voltage drop as possible). In your current system, you might be seeing the battery being cycled way more than you would have expected when on shore power.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    #3
    Re: Balancing Battery Charger, Solar Controller, and Trimetric
    BB. wrote: »
    I am not quite sure I understand...

    -Bill
    Was trying to keep it short but got confusing in doing so.

    Currently, running the generator, I charge via the woefully inadequate WFCO 8955 converter/charger which additionally is 15' away one way via 10awg. Woefully? Let me explain. Many people have attempted to get the WFCO to go into bulk (14.4 volts) and failed so I'm stuck with a maximum 13.6 Volts @ 55 amps max at the converter output. What actually get's to my battery will never charge it in a day. Could I run a new 4 or 2 gauge to the batteries? Sure but I still have a less than adequate charger. I thought about a good three stage charger but could I run that dude all day then into the evening? The PD9245 is a RV converter/charger with filtered power and is designed to run the camper for days on end when plugged into shore power. It has 4 stage charging with some manual control and a reportedly quite advanced wizard that does a good job charging batteries.

    Here's the deal, I want to have the option of charging my RV's battery bank either from the PD or solar and not confuse the Trimetric. The P1, P2, and P3 settings need to jive correct?

    If you look at my sig pic the batteries are right behind the propane tanks and my converted power closet is at the extreme right front corner of the camper via an external access door. I have two 7 foot 6 awg custom built cables coming that will terminate in the power closet to a shunt and power distribution point. I'm running another 6 awg cable 2 foot long back out of the closet to the frame from the other side of the shunt. My solar controller will be in this closet and I was thinking I would put the PD9245 in there. Both charging sources would be the same distance from the batteries. Since the solar controller is fully adjustable I would need to log a full discharge/charge cycle of the PD then set the P1, P2, and P3 accordingly then bring the solar controller in line.

    Jeff
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Balancing Battery Charger, Solar Controller, and Trimetric

    The Trimetric measures current going in to and out of the battery. It doesn't care where the current comes from or goes to or at what Voltage. So long as all loads and charge sources are on one side of the shunt and the batteries are on the other it will work.
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  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    #5
    Re: Balancing Battery Charger, Solar Controller, and Trimetric
    Cariboocoot wrote: »
    The Trimetric measures current going in to and out of the battery. It doesn't care where the current comes from or goes to or at what Voltage. So long as all loads and charge sources are on one side of the shunt and the batteries are on the other it will work.
    So the P1, P2, and P3 settings are not important??
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: Balancing Battery Charger, Solar Controller, and Trimetric
    unyalli wrote: »
    So the P1, P2, and P3 settings are not important??

    Not as far as the battery monitor is concerned.
    The batteries themselves might have a different opinion on the matter if they don't get to the Voltage level they want (take too long to fully recharge, insufficient remix of electrolyte).

    Whereas it is ideal to get the charging set points of multiple charge sources to agree, it is not essential. When used concurrently any with lower Voltage settings will contribute to Bulk stage and then may just 'Absorb" without contributing anything. The best way to do this with multiple solar sources is to make sure the controller with the largest array is the one with the proper (highest) Voltage settings; the "lesser" ones add to the Bulk charge and then just go along for the ride.

    You should be able to achieve similar results with different charge sources of different types (i.e. engine alternator, gen-powered charger, solar).
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