I am looking to put in a solar system that will produce about 30 amps per day. I choose a semi-flexible 135 watt panel made by Sunpower which meets my capacity needs.My only problem is choosing the charge controller. My original choice was a 20 AMP Suntracer MPPT (yes it is a REAL MPPT) with the remote panel.My only issue is that I want to use the see consumption and use the low voltage battery disconnect, unfortunately my converter is 55 AMPs. If I want a 55 AMP or more charge controller the cost goes up obscenely. Realistically, what is the maximum draw I can see from 12V lights, heater fan, and other 12V loads. I know it is hard to estimate but what is typical?Also, does the converter ever supply 55 amps for battery charging? Thank you.

12v amperage usage in RVI suppose your converter could pump 55a if the wire to the batteries is big enough.

Hi skripo, Do you mean 30 amp-hours of solar harvest per day?

Per NEC for 30 amps of solar you will need a 45 amp controller; NEC derates them to about 36 amps. Our worst case boondocking usage takes the batteries to 47% state of charge in one day. That is ~662 WH. We are very conservative and normal usage is ~189 WH. A quick and dirty rule of thumb 100 watts of solar per 100AH of battery, but the reality is more complicated.

skripo wrote:I am looking to put in a solar system that will produce about 30 amps per day. I choose a semi-flexible 135 watt panel made by Sunpower which meets my capacity needs.30AH/day would be typical with one 135W module, maybe a bit more if the sun is good.My only problem is choosing the charge controller. My original choice was a 20 AMP Suntracer MPPT (yes it is a REAL MPPT) with the remote panel.I know squat about that controller but is sems to have a rating large enough to handle a single 135W module.My only issue is that I want to use the see consumption and use the low voltage battery disconnect, unfortunately my converter is 55 AMPs. If I want a 55 AMP or more charge controller the cost goes up obscenely. Don't understand the thoughts, here. Please try again.Realistically, what is the maximum draw I can see from 12V lights, heater fan, and other 12V loads. I know it is hard to estimate but what is typical?Download this spreadsheet calculator and add up your total:Quartzfest calculatorAlso, does the converter ever supply 55 amps for battery charging? Yes, it's possible that a 55 amp converter delivers 55 amps at the output terminals. You will need adequate cable, a battery that will accept the amps, and a circuit breaker between battery and converter greater than 55 amps (some are only 30 amps)Thank you.Hope it helps

Thank you for all the replies.Pianotuna: I think so. I have this battery and it is 50% after 2 days of use.Westend: Thank you for the calculator. Some converters have a consumption meter and an LVD function that disconnects the battery when it drops below a certain voltage.Unfortunately the charge controller needs to sit between the battery and the load to do this and has to be sized to the load amperage.I am assuming that worst case scenario would be 55 amps because that is my panels rated amperage.

Solar charge controller selection help needed | Good Sam Community

skripo
Explorer
May 05, 2015
Thank you for all the replies.

Pianotuna: I think so. I have this battery and it is 50% after 2 days of use.

Westend: Thank you for the calculator. Some converters have a consumption meter and an LVD function that disconnects the battery when it drops below a certain voltage.

Unfortunately the charge controller needs to sit between the battery and the load to do this and has to be sized to the load amperage.

I am assuming that worst case scenario would be 55 amps because that is my panels rated amperage.
westend
Explorer
May 05, 2015
skripo wrote:
I am looking to put in a solar system that will produce about 30 amps per day. I choose a semi-flexible 135 watt panel made by Sunpower which meets my capacity needs.

30AH/day would be typical with one 135W module, maybe a bit more if the sun is good.

My only problem is choosing the charge controller. My original choice was a 20 AMP Suntracer MPPT (yes it is a REAL MPPT) with the remote panel.
I know squat about that controller but is sems to have a rating large enough to handle a single 135W module.

My only issue is that I want to use the see consumption and use the low voltage battery disconnect, unfortunately my converter is 55 AMPs. If I want a 55 AMP or more charge controller the cost goes up obscenely.
Don't understand the thoughts, here. Please try again.

Realistically, what is the maximum draw I can see from 12V lights, heater fan, and other 12V loads. I know it is hard to estimate but what is typical?
Download this spreadsheet calculator and add up your total:Quartzfest calculator

Also, does the converter ever supply 55 amps for battery charging?
Yes, it's possible that a 55 amp converter delivers 55 amps at the output terminals. You will need adequate cable, a battery that will accept the amps, and a circuit breaker between battery and converter greater than 55 amps (some are only 30 amps)

Thank you.

Hope it helps
scrubjaysnest
Explorer
May 05, 2015
Per NEC for 30 amps of solar you will need a 45 amp controller; NEC derates them to about 36 amps. Our worst case boondocking usage takes the batteries to 47% state of charge in one day. That is ~662 WH. We are very conservative and normal usage is ~189 WH. A quick and dirty rule of thumb 100 watts of solar per 100AH of battery, but the reality is more complicated.
pianotuna
Nomad III
May 05, 2015
Hi skripo,

Do you mean 30 amp-hours of solar harvest per day?
2oldman
Explorer II
May 05, 2015
12v amperage usage in RV

I suppose your converter could pump 55a if the wire to the batteries is big enough.

Forum Discussion

Solar charge controller selection help needed

About DIY Maintenance

Related Content

Battery charge controllers

MPPT solar charge controller recommendaion

new tire selection

Ram selection

Difference in solar charge controllers