Solar panel AGM battery regulator question

[tymonk]

Hello. I am still trying to find out the wiring in my new-to-me boat as the former owner (an electrical engineer) died. It seems there are 2 relatively small panels that each seem to be directly connected with a fuse to a battery each. I think they serve the purpose of trickle chargers (based on size I think they’re 5W-20W) and should probably be upgraded recharge for more significant use/trips. However, in the near term I won’t go on more than day trips so just want to ensure the batteries don’t go flat on the swinging mooring. I swapped out the batteries which were dead to AGM batteries. I left the smallest panel connected to one of the batteries (I read somewhere small 5W panels have low risk of overcharging) and it read over 15v after a week which is no good. My thought was to install a cheap/small regulator for now, and then swap out the panels later. My question:
- can both panels be directly wire into a regulator? I.e. insert 2 pos and 2 neg wires directly into the screw in slots
- can anyone recommend a specific controller? I am told AGM batteries need to charge at 14.6-14.8v and should not have an “equaliser” phase which is above this as can drastically reduce their life time
- for replacement panels in the long term, does anybody know any narrow panels around 65 x 20-25cm? This would allow me to maximise the space on the companion way hatch cover hangar. The only ones I can find are the dodgy looking ones on eBay listed as everything from 30-80W for the same size which is obviously not right.

Any help, as ever, is most appreciated.

 

[Graham376]

Yes, you can parallel the two panels. A Victron Smartsolar mppt regulator will allow you to input the correct charging regime for your batteries.

 

[William_H]

A 5w panel should give a max .25 amp in full sun. Makes me wonder if your 15v measured is correct. Was it at the battery terminal and is the meter accurate. Small panels should be fine without a regulator. This assuming you have a 100AH or so battery.
However if you want to go regulator an MPPT type would be best with both panels in series or parallel but then you need to get one with 2 outputs or feed just one battery or both connected in parallel.
Re "dodgy" panels on ebay. I like the ones encapsualated in resin, no ali frame but really I think all are OK. (cheap is good) ol'will

 

[ltcom]

Hello. I am still trying to find out the wiring in my new-to-me boat as the former owner (an electrical engineer) died. It seems there are 2 relatively small panels that each seem to be directly connected with a fuse to a battery each. I think they serve the purpose of trickle chargers (based on size I think they’re 5W-20W) and should probably be upgraded recharge for more significant use/trips. However, in the near term I won’t go on more than day trips so just want to ensure the batteries don’t go flat on the swinging mooring. I swapped out the batteries which were dead to AGM batteries. I left the smallest panel connected to one of the batteries (I read somewhere small 5W panels have low risk of overcharging) and it read over 15v after a week which is no good. My thought was to install a cheap/small regulator for now, and then swap out the panels later. My question:
- can both panels be directly wire into a regulator? I.e. insert 2 pos and 2 neg wires directly into the screw in slots
- can anyone recommend a specific controller? I am told AGM batteries need to charge at 14.6-14.8v and should not have an “equaliser” phase which is above this as can drastically reduce their life time
- for replacement panels in the long term, does anybody know any narrow panels around 65 x 20-25cm? This would allow me to maximise the space on the companion way hatch cover hangar. The only ones I can find are the dodgy looking ones on eBay listed as everything from 30-80W for the same size which is obviously not right.

Any help, as ever, is most appreciated.

If your batteries are really being overcharged at present [and I cant see how a small panel of 5W can charge abattery to 15V] why not buy a cheap regulator £7 on ebay that stops charging at 14.4v [default] can be changed to 14.6V. Wont be MPPT. i dont know your pocket. MPPT is good but you say only going on day trips, so MPPT is expensive overkill? Yes can wire in parallel...... keep the fuse in line just incase. If batteries are being overcharged already, why buy bigger panels?

 

[sailaboutvic]

I wouldn't waste £10 or £20 on a cheap regular,
if your plainning to get better and bigger panels , buy a MPPT and if you can afford it one with Bluetooth that way you be able to see what's going on without having to get the meter out and going to the batteries .

 

[tymonk]

Yes, you can parallel the two panels. A Victron Smartsolar mppt regulator will allow you to input the correct charging regime for your batteries.

Thanks. Could you run 2 leads straight from the controller to the batteries? Alternatively have found a dual charger like this one:PV Logic 15A Smart MPPT Charge Controller

 

[tymonk]

I wouldn't waste £10 or £20 on a cheap regular,
if your plainning to get better and bigger panels , buy a MPPT and if you can afford it one with Bluetooth that way you be able to see what's going on without having to get the meter out and going to the batteries .

Thanks. Any suggestions besides Victron? Potentially cheaper ?

I do have permanent BT monitors on the batteries

 

[tymonk]

If your batteries are really being overcharged at present [and I cant see how a small panel of 5W can charge abattery to 15V] why not buy a cheap regulator £7 on ebay that stops charging at 14.4v [default] can be changed to 14.6V. Wont be MPPT. i dont know your pocket. MPPT is good but you say only going on day trips, so MPPT is expensive overkill? Yes can wire in parallel...... keep the fuse in line just incase. If batteries are being overcharged already, why buy bigger panels?

Do you have a link to any of these regulators that can be set to 14.6-14.8? Could be good intermediary solution and then buy MPPT as part of a kit later. Can the batteries similarly be wired in parallel directly to the regulator? The fuses are on this end.

 

[sailaboutvic]

Thanks. Any suggestions besides Victron? Potentially cheaper ?

I do have permanent BT monitors on the batteries

There load around but I now tend to stick to victron

 

[vyv_cox]

I charged the 2 x 130 Ah domestic bank on my motorsailer for 2 years with a 20 watt panel, no regulator, perfectly safely in North Wales. Due to medical issues the boat was rarely visited but each time the voltage was around 14, certainly never came near 15 volts .

 

[Tinto]

I have a renogy mppt controller with BT and solar panels. The MPPT feeds a Victron charger which was already on the boat.

The renogy kit gets decent reviews and is not expensive.

 

[Graham376]

Thanks. Could you run 2 leads straight from the controller to the batteries? Alternatively have found a dual charger like this one:PV Logic 15A Smart MPPT Charge Controller

Not sure what your battery setup is. If you have separate starter and domestic, then not a good idea to parallel them for charging from one regulator. If one battery goes down it will take the other out so, better to have a dual output regulator or, as I do, just charge the domestic bank as the isolated engine battery will last for months without charging. Many of the cheap Chinese regulators are not as described and, with previous bad experience, I wouldn't fit anything I can't program to suit batteries installed.