Battery - Different amp rating combine.

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Battery - Different amp rating combine.

Postby harrydiculous » Thu Dec 05, 2019 4:38 pm

Hi

I've been offered a 200 amp/hr 12 volt deep cycle battery. (I *think* it's an AGM) It's from a backup system, kept fully charged. They are replaced every two years regardless.

I currently run 4 x 100 amp/hr deep cycle flooded batteries in parallel (12 volt system).

It's probably not "best practice" but it will save me about $450 as I don't want to expand it beyond 600amp/hr at this stage.

Any issues with this?

Thanks

Graeme
3kW on grid. Solar River PV Grid Tied inverter 3000TL. Rene Solar Panels 12 x 250. Solar Hot Water. 960 watt Solar off grid with 3500 watt inverter. 4 x 100 amp/h batteries.
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Re: Battery - Different amp rating combine.

Postby davef » Thu Dec 05, 2019 7:21 pm

The first thing that popped into my mind was equalisation:

https://discoverbattery.com/EN/battery-101/general-charging-information-for-agm-and-gel-batteries/

See the warning about 1/2 way down.

The float voltages are probably slightly different, don't know whether or not that will affect the lifetime of battery.

It involves labour but if you can control when equalisation takes place maybe just disconnect the AGM.
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Re: Battery - Different amp rating combine.

Postby harrydiculous » Thu Dec 12, 2019 11:42 am

Thanks Dave. I'll fit it then. It should be coming next week. I did read somewhere that maybe some diodes can be fitted to control it, but no method was given. I can't remember where I saw this now, anyway.
3kW on grid. Solar River PV Grid Tied inverter 3000TL. Rene Solar Panels 12 x 250. Solar Hot Water. 960 watt Solar off grid with 3500 watt inverter. 4 x 100 amp/h batteries.
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Re: Battery - Different amp rating combine.

Postby jaahn » Fri Dec 13, 2019 8:37 am

Hi Graeme :)
My suggestion would be to make the battery connections between the new one and the others so you can easily disconnect it. Then you can check the charge of both seperately and also charge them seperately occasionally to get them fully charged up to their own specs. That should help to keep them going as best as possible.
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Re: Battery - Different amp rating combine.

Postby harrydiculous » Fri Dec 13, 2019 10:24 am

Thanks Guys. I'll await my donation.
3kW on grid. Solar River PV Grid Tied inverter 3000TL. Rene Solar Panels 12 x 250. Solar Hot Water. 960 watt Solar off grid with 3500 watt inverter. 4 x 100 amp/h batteries.
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