I have a 2000 watt inverter charger running off 4 GCU 6 volt, fully charged golf cart batteries. High load appliances like the microwave quickly cause a low voltage overload. I have 2/0 cables from the inverter to the first pair of batteries and they are less than 3 feet in length. They are wired to the nearest pair. The batteries are connected with #2 awg cables. Given the price of flexible copper welding cable I am reluctant to build new cables for the batteries unless I know it is going to make a big difference. If we really need the microwave, I can fire up the Honda but I would like to be getting the 2000 watts off the inverter.(I am also toying with getting an inverter microwave to run at lower power as an alternative.)

They are wired to the nearest pair. The batteries are connected with #2 awg cablesi would up the gauge of the wire between the batteries and if the batteries are all next to each other it should help to connect the inverter + to one pair of batteries and - to the other pair to balance the load better between all the batteries

"First pair" sounds like the bank is not balanced by having the load across the whole bank, but instead you have a "downstream" pair that takes less than half the load. It should not be that bad though with those wires, so it could be the batteries. Have you checked each cell in all four with an hydrometer?

Get out the voltmeter and verify the situation.Put the meter right on the inverter input terminals, note how much the voltage drops when inverter starts running. Do the same right on the battery terminals. Post the results.Depending on the situation move the meter to detect at different places to verify connections are good.Not sure how far the pairs are apart but this could be the issue. The near pair is probably over worked. May need to wire the near pair in parallel and then connect in series with the second pair also in parallel. The full series connection should be 2/0.If the wiring is not changed, the close pair will be overworked even if the inverter-microwave resolves the issue with lower amps draw.

Thanks for your replies. Yes, I regularly check the cells with a hydrometer and all are good. The voltage at the inverter drops to 11.8 which is where it will drop off line.I built the wiring 20 years ago without a large inverter in mind. The price of flexible welding cable has jumped a bunch. Just was quoted $6.89 a foot for 0/2 flexible! I will ponder the options and do whatever makes sense. Thanks again.

voodoo101 wrote:Thanks for your replies. Yes, I regularly check the cells with a hydrometer and all are good. The voltage at the inverter drops to 11.8 which is where it will drop off line Your microwave could cause a 150A battery draw which is significant. 2x 2/0 3' cables will drop the voltage about 0.1V so the rest is connections and batteries. Check each cable voltage end to end under load. Load test your batteries as they could be weak. Unbalanced loading causes more usage on the nearest pair and shorter life. Also can you lower the cutoff voltage on the inverter?

battery to inverter wiring | Good Sam Community

shastagary
Explorer
Jun 17, 2022
They are wired to the nearest pair. The batteries are connected with #2 awg cables

i would up the gauge of the wire between the batteries and if the batteries are all next to each other it should help to connect the inverter + to one pair of batteries and - to the other pair to balance the load better between all the batteries
BFL13
Explorer II
Jun 17, 2022
"First pair" sounds like the bank is not balanced by having the load across the whole bank, but instead you have a "downstream" pair that takes less than half the load. It should not be that bad though with those wires, so it could be the batteries.

Have you checked each cell in all four with an hydrometer?
time2roll
Nomad
Jun 17, 2022
Get out the voltmeter and verify the situation.

Put the meter right on the inverter input terminals, note how much the voltage drops when inverter starts running. Do the same right on the battery terminals. Post the results.

Depending on the situation move the meter to detect at different places to verify connections are good.

Not sure how far the pairs are apart but this could be the issue. The near pair is probably over worked. May need to wire the near pair in parallel and then connect in series with the second pair also in parallel. The full series connection should be 2/0.

If the wiring is not changed, the close pair will be overworked even if the inverter-microwave resolves the issue with lower amps draw.
voodoo101
Explorer
Jun 17, 2022
Thanks for your replies. Yes, I regularly check the cells with a hydrometer and all are good. The voltage at the inverter drops to 11.8 which is where it will drop off line.

I built the wiring 20 years ago without a large inverter in mind. The price of flexible welding cable has jumped a bunch. Just was quoted $6.89 a foot for 0/2 flexible! I will ponder the options and do whatever makes sense. Thanks again.
CA_Traveler
Explorer III
Jun 17, 2022
voodoo101 wrote:
Thanks for your replies. Yes, I regularly check the cells with a hydrometer and all are good. The voltage at the inverter drops to 11.8 which is where it will drop off line
Your microwave could cause a 150A battery draw which is significant. 2x 2/0 3' cables will drop the voltage about 0.1V so the rest is connections and batteries. Check each cable voltage end to end under load. Load test your batteries as they could be weak. Unbalanced loading causes more usage on the nearest pair and shorter life.

Also can you lower the cutoff voltage on the inverter?
theoldwizard1
Explorer II
Jun 17, 2022
How many feet of 2/0 are we talking, 3', 6' (x2). Pay the money. There are places on eBay that will make up whatever you want with the proper ends.
3_tons
Explorer III
Jun 17, 2022
Cabling is your bottleneck, a very common problem that causes grief for the poor 2000w inverter…Early on, I learned this the hard way, but now likely a bit overkill at 0004, 3’ with silver soldered and crimped copper lugs, but no more inverter alarms!!

3 tons
voodoo101
Explorer
Jun 17, 2022
3 tons wrote:
Cabling is your bottleneck, a very common problem that causes grief for the poor 2000w inverter…Early on, I learned this the hard way, but now likely a bit overkill at 0004, 3’ with silver soldered and crimped copper lugs, but no more inverter alarms!!

3 tons

Got it. Thanks all.
2oldman
Explorer II
Jun 17, 2022
I recommend higher voltage, like at least 24 for high draw stuff, but too late for that. Your inverter manual may specify 4/0 for that load. #2 may be a bit small for the interconnects.
BFL13
Explorer II
Jun 17, 2022
11.8v shut off is ridiculous. Most straight inverters alarm at 11v but keep running until 10.5v shut off. You have an inverter/charger which might have settings so perhaps you can change that as suggested above.

If you have a 1v voltage drop with MW on, now you need 12.8 battery voltage to get anything. How when a full battery is 12.7?

EG I have a 1v drop with MW on, but my inverter alarms at 11v so I can run it when battery is below 50% SOC at 12.1v. Your wiring is fatter than mine and we both have four 6s.

Edit: do you have some other thing in the circuit that shuts off at 11.8? Not sure how they work, but some monitors like Victron have a way to do that?