battery switches

Discussion about the OutBack Energy Cell Batteries
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sod0499
Forum Junior Member
Posts: 2
Joined: Wed Jun 20, 2018 2:24 pm
My RE system: 48VDC, twin 2,500 watt inverters
(9) JAP6(k) 315 watt panels
flexmax 80 charge controller
(8) Trojan 6 volt, 375 Ah AGM batteries

battery switches

Post by sod0499 » Wed Jun 20, 2018 2:32 pm

I recently purchased a new set of batteries for my off-grid system. The old set, though 12 years old, still has strong performance. A suggestion was made to install a battery switch to switch from the new bank to the old bank and, thus, still utilize the capacity of the old bank. Apparently, this is a common approach with boat batteries. Does anyone have any experience (or opinion) with this approach in a solar system? Obviously, the size of the battery is significantly larger.

JRHill
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My RE system: -House: FM 80, VFX 3648, FlexnetDC, FlexWare xformer, Mate 3 / Hub, WattPlot/, 2925w SunTech 195, Trojan L16RE-B Batteries. Backup 1: Honda EU7000is w/2 wire auto start via FM80 aux, backup 2: 11kw Miller Bobcat;
-Well: Grundfos 11-SQF-2 pump, controller & AC switch (CU200, IO101), Tristar 45 Controller, 780w SunTech 195, Trojan golf cart batteries.
-All running since July '11 with various upgrades and workarounds.
Location: South central WA
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Re: battery switches

Post by JRHill » Fri Jun 22, 2018 8:33 am

I pondered this question when I replaced my batteries a few years back because, like you, the old batteries still had service life. At that time I also added a FNDC and a Mate3. I ultimately dismissed the idea for two reasons: 1) the FNDC and, 2) charging complications. If I were to switch to a charged bank then I am leaving the other in a discharged state - not good. Since the value of the reserve would be in the winter when I'm using generator power anyway I'd just be making things more complex and doing a disservice to all of the batteries.

But I still didn't want to return usable batteries just for the core charge. So I put an add in the local paper and got an immediate call from someone who was trying to live off grid but couldn't afford adequate, new batteries. I ended up with about half the value of a new set of L16 in trade for 5 rolls of very expensive fence that he had to trade. We both came out well.

The down side was the fence had to be built (wink).

Vic
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Location: San Joajuin County, CA

Re: battery switches

Post by Vic » Fri Jun 22, 2018 10:46 am

sod0499 wrote:I recently purchased a new set of batteries for my off-grid system. The old set, though 12 years old, still has strong performance. A suggestion was made to install a battery switch to switch from the new bank to the old bank and, thus, still utilize the capacity of the old bank. Apparently, this is a common approach with boat batteries. Does anyone have any experience (or opinion) with this approach in a solar system? Obviously, the size of the battery is significantly larger.
Battery switches are commonly-used on 12 V systems, and sometimes on 24 V systems, but, generally, the Maximum voltage rating to the "1 -> 2, 1 + 2, Off" switches (which you would probably want), have a Maximum voltage rating of 32 V. Have seen a single bank, ON , Off switch that has a Max voltage rating of 48 V, but this is just too low a voltage rating for LA batteries.

Those 12 year-old batteries may have less Capacity than you are guessing ...

FWIW, Vic
4/20/08: 18 Shell SQ 175-106 Vmpp, Stacked 5548 SW+, 1350 AH Surrette 4KS25's, MX-60, Kubota SQ-3250 25 KVA Polyphase Diesel genset. Thanks OutBack for this Forum + the great Support and Service.

sod0499
Forum Junior Member
Posts: 2
Joined: Wed Jun 20, 2018 2:24 pm
My RE system: 48VDC, twin 2,500 watt inverters
(9) JAP6(k) 315 watt panels
flexmax 80 charge controller
(8) Trojan 6 volt, 375 Ah AGM batteries

Re: battery switches

Post by sod0499 » Mon Jun 25, 2018 6:39 am

Thanks for your thoughts. One additional factor that might be relevant is that my system is overpowered with panels. So, I should be able to recharge both battery banks in a day of sun. I am just trying to keep from using batteries that are down to 50% state of charge from the evening's usage.

What does FNDC stand for?

Lastly, I will check the voltage rating on the battery switch. Clearly critical.

Boyd

jbakker
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Joined: Fri Feb 23, 2018 6:47 am
My RE system: 2 VFX3648 Inverters 2 FM60 150VDC Charge Controllers Mate3 3.4 KW of panels 15kw JC Onan NG Generator made in 1975 I love that generator almost as much as my wife.
7 banks of 14 cells each from a 2017 Chevy Volt. Parallel for the AMP Hour. 7 Chinese made BMS systems.
Location: Goderich Ontario Canada

Re: battery switches

Post by jbakker » Tue Jun 26, 2018 4:15 am

This is what a FNDC is.

http://www.outbackpower.com/products/sy ... flexnet-dc


Allows you much more detail in what is going in and out of your batteries.

Lots of info here on the the units. Do a search.

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