Battery Voltage Question

[cwe123]

I replaced my old battery with a West Marine brand for my old Mako with an Evinrude 88 SPL. When I got it voltage was high (~14v) but after a month and a half with the new battery it's usually down to about 12.4v when I get on the boat. Whenever I leave it at the dock I shut off everything (GPS, FF, trim relay, lights) and just leave 1 auto bilge pump switched on which checks every few minutes for prime (non self-bailing boat).

I have checked and the pump uses barely any power even for a week at a time between running the boat. What can I do to keep the voltage high? I haven't had any issues starting the engine but I am afraid that voltage is too low. I don't have an onboard battery charger/shorepower but I do have a portable battery charger - would it be worth it to charge my boat battery up with that and see what happens? I'd appreciate it if anyone could shed some light on this.

Thanks.

 

[sutor623]

Re: Battery Voltage Question

Depends if that charger has a trickle charge or not. If it is a smart charger you could. But to be 100% honest, no matter how high a battery gets during charging, the voltage will drop to about 12.7ish volts. Usually this takes a few hours. If you have a charge at 12.4volts after a week I think you will be fine. Thats pretty good. I have a small 12v solar panel that has battery clips on it, bought it for $20 a few years back. It does .5amps per hour. Something like that would help to keep the battery topped off without having to run power to the boat while it is in the slip.

 

[bruceb58]

Re: Battery Voltage Question

You want to measure the voltage of the battery when its been sitting for over 30 minutes after any charge voltage has been removed. If you measure the voltage too soon, you will be measuring the surface charge and your measurement won't be accurate.

12.6V is a fully charged battery.

 

[cwe123]

Re: Battery Voltage Question

Ok guys, so I have an update. I was on vacation and didn't use the boat for about 9 days - when I left the voltage was at around 12.3v and upon returning and using the boat I was just under 12v - the motor wouldn't start. I was able to charge it up with the portable battery charger and get running but I need to find out a solution.

I bought a 1W solar trickle charger so my plan is to charge the battery up to where it's supposed to be (go for a long run) and then hook up the solar charger when returning to the slip. Does this sound like a good solution?

 

[bruceb58]

Re: Battery Voltage Question

You need to charge it up fully before you leave it that long. 12.3V is only 70% charged. It also shouldn't be discharging that much by itself for 9 days unless there is a draw on the battery.

I just read your first post again. If your auto bilge pump is the type that doesn't use a float switch and runs itself every once in awhile to see if there is water, that is your problem. Get rid of that bilge pump. They are battery killers,

 

[sutor623]

Re: Battery Voltage Question

You need to charge it up fully before you leave it that long. 12.3V is only 70% charged. It also shouldn't be discharging that much by itself for 9 days unless there is a draw on the battery.

This,

I bought a 1W solar trickle charger so my plan is to charge the battery up to where it's supposed to be (go for a long run) and then hook up the solar charger when returning to the slip. Does this sound like a good solution?

and yes.

 

[cwe123]

Re: Battery Voltage Question

I will swap out that auto pump over the winter - I think part of the issue is that I really don't travel very long distances therefore don't give the battery a chance to charge up. I usually run a 1/2 mile from my slip and anchor up in the cove or run out about a mile to fish.

To bring it back to full charge could I just hook up the battery to my portable charger for a few hours or would it be better to just drive the boat? Thanks all for the replies.

 

[snowbrd84]

Re: Battery Voltage Question

You could put in a second battery, connect it to the primary battery with a disconnect and hook the bilge pump to the second battery. Just switch the disconnect whenever you park the boat for a long period. Bilge still has power, but the primary starting battery stays fresh for when you need to start the boat. Then just reengage the disconnect after you start the boat to replenish the secondary battery...

 

[bruceb58]

Re: Battery Voltage Question

To bring it back to full charge could I just hook up the battery to my portable charger for a few hours or would it be better to just drive the boat? Thanks all for the replies.

Depends on how discharged your battery is and how much current you battery charger charges the battery at.

Your outboard motor probably has a very low output charging circuit so I wouldn't rely on it doing much.

 

[cwe123]

Re: Battery Voltage Question

Update: Eventually I wasn't able to start my boat even with a portable battery jumper attached to my battery. Since I bought it in June I decided to remove the battery and bring it to West Marine to be tested - they said the machine gave it a zero health rating and that it should be replaced - they gave me a new one.

Now my question is, can I leave my solar panel connected to the battery all the time even when I'm running the boat? It will be a pain to remove the fuse and disconnect the cable every time I want to go out - is there any risk associated with leaving the panel connected while the engine is running?

 

[bruceb58]

Re: Battery Voltage Question

You can leave your solar panel connected.

 

[Silvertip]

Re: Battery Voltage Question

Couple things come to mind here. 1) If you took a deeply discharged battery to be tested it should fail. Batteries need to be charged and then load tested. If they are already dead, obviously the test will fail. 2) You said you have a 1 Watt solar panel. You do realize that panel is virtually worthless as it would never, ever, top off a battery. It simply does not have enough capacity. You need as a minimum a 5-7 watt panel to supply any meaningful current. 1 watt = .079 amps which would hardly light light a single LED. As an example, if your bilge pump drew 6 amps for 5 seconds during it's "periodic test", you should be able to comprehend how long it would take that panel delivering .079 amps PER HOUR to replace that power. In my view that is not a solution to the problem. A bigger panel is and it is also a target for thieves.

 

[cwe123]

Re: Battery Voltage Question

Couple things come to mind here. SNIP

So the 1W panel won't maintain a battery with no load?

 

[bruceb58]

Re: Battery Voltage Question

Barely. You sure its only 1W? I figured it was just a mistype before. If so, its pretty much useless.

 

[sutor623]

Re: Battery Voltage Question

Barely. You sure its only 1W? I figured it was just a mistype before. If so, its pretty much useless.

I'm thinking he meant 1 amp. I have a small .5 amp charger that I used to use on my old car. There was a short somewhere that I couldn't find and I got tired of pulling the negative wire everytime I parked the car. Kept the battery charged just fine.

And cwe I think that you will fry that solar panel if you leave it connected. Do you have a 12vdc port like the vehicles have? I used to just plug my solar panel into that and leave the panel on the dash. Just unplug it and roll out.

 

[bruceb58]

Re: Battery Voltage Question

Almost all solar panels have a diode in them that would prevent damage. If you don't have that diode, you would also discharge the battery at night.

 

[cwe123]

Re: Battery Voltage Question

The panel is 1W and is designed to maintain a battery not charge it. It has a diode to prevent overcharging. The one I got is Amazon.com: Sunforce 50013 1-Watt Motorcycle and Powersports Solar Battery Charger: Automotive

 

[bruceb58]

Re: Battery Voltage Question

Like I said before, you can keep it connected. It won't be charging it much, if at all. Doesn't sound like you expected that anyway.

 

[Silvertip]

Re: Battery Voltage Question

The diode does not prevent overcharging. That cannot happen with a 1 watt panel. It's puepose was just described. Did you not see tne motorcycle part of that description. Those are very small batteries and a 1 watt panel is still worthless on it.

 

[cwe123]

Re: Battery Voltage Question

Just so I understand, that panel I have won't do anything in terms of keeping the battery topped up even if I leave the boat for several weeks without running it?

Should I get a bigger panel say 5 Watts to accomplish this? Again there will be no load on the battery when the boat sits in my slip. The battery is a Seavolt/West Marine Starting 650, it's about the size of a car battery.