Battery State of Charge indicator

S

ssobol

Active member
There have been discussions in this forum of the state of charge of the batteries. Since I usually anchor out and don't have a generator I find that sometimes I get a low voltage indication in the middle of the night (the CO detector starts going off when the voltage is too low).

I was thinking it might be nice to have a SOC indicator for both batteries so I can monitor the voltage and maybe top them up before turning in for the night.

I've seen battery level indicators online but they are simple voltmeters. Can anyone recommend a decent SOC indicator (that's a bit more accurate than just a voltmeter) at a reasonable cost?
 
I have nothing but good things to say about the Victron BMV600S I installed. I've had battery monitors the the past (other brands/models), and they all have worked great and give (to me) priceless information.

The reason I went with the Victron this time around is that, in addition to getting a good review from a persnickety electronics person who has used many different ones over the years, it is also refreshingly easy to install. For the "small" wiring, instead of numerous little wires to connect, it has one "Cat 5" type of plug. Not a huge big deal, as you only wire it once, but... it tipped the balance in favor of it for me.

It's a ~2" round gauge that either "self trims" or it also comes with a square bezel if one prefers that (allows a bit more latitude in hole size). I used the plain round one.

It does other handy things too, such as tell you just what you are drawing, in amps (so you also can measure various things to see what they draw)

I got mine for around $149 from Jamestown Distributors.

51843.jpg

(The blue light does not have to be on all the time.)

Sunbeam

PS: I was just about to post this in another thread where we were talking about it, but one "gotcha" that I have to correct: When we got out on the water, both my friend and I had lots to do ("new" boat/gear stuff), and he happened to be the one who calibrated the Victron (easy to do, but it's calibrating it that gives you the SOC percent). Well, not knowing that an outboard (at least from what I have read) really never gets the batteries up to 100%, he waited until the battery wasn't accepting any more charge (from the outboard) and then calibrated.

Well, I wondered why my outboard was so special that it was "easily" getting the SOC up to 100% (not that I was complaining but... really?) Then the penny dropped. Duh! I think we'll have to re-calibrate after my "land" charger gives it a "real" 100% charge (very easy to do though).
 
This summer I added a Victron 602S - it's very similar to the 600, except it also allows monitoring of a second battery. The second battery only shows voltage (not all the other info available for the "primary" battery). I have the house bank as my primary to keep track of all the good info it provides and connected the single starting battery as secondary for the monitor. I wish the monitor provided all the details for both banks, but only the voltage for the start battery is helpful nonetheless.

I especially like the ability to conveniently isolate and verify/document the draw for each component connected to my house bank. As Sunbeam indicated, installation was straightforward.

Les
 
I used to worry about battery drain from the overhead lights...then I bought a number of LED replacements off EBAY .....under $4 each ...they have the regular bulb base on them and something like 48 led lights...took minutes to install and really reduced the current drain from the batteries....

SEA3PO
 
I already replaced most of the incandescent lights with LEDs.

I checked the current draw of one of the incandescent bulbs from the Perko lights with the LED replacement (48 LED pad). The current draw of the LEDs was about 1/4 the bulb, not the 1/10th most people quote. This is because it takes many more LEDS to put out the same amount of light as one incandescent bulb.

Still, 1/4 the current draw is still a big improvement.
 
If you are having low battery indications, there is a good chance you are not doing the batteries any favors. You may want to look at larger house bank batteries--going to group 31 batteries. If you have group 24 battery currently it will be about 80 amp hours and a group 31 would be closer to 110 amp hours.

I happen to use a Link Lite battery monitor; it is about the same as the Victron 6025 (with the second battery voltage only monitor).

Generally we only get our batteries up to about 85 % of capacity with the outboard charging--and that last 15% comes with the long charge at the dock.
 
I don't know how old the batteries are or the size. Right now I don't have access to my boat to check.

The boat has an on-board battery charger. When I am able to, I charge the batteries with this charger about once a month. The rest of the time the engine alternator to charges the batteries when we are cruising.
 
My Garmin GPS has a voltage screen that you can adjust for many user views. It also has an alarm set point that you can set to alarm if voltage goes below your chosen voltage level. I use it check the state of the batteries when motor is off. Only down side is GPS must be on to check but it is FREE.
Pete
Pompano
 
The difference between the battery monitors and GPS, is that the monitor take the voltage right off the battery terminal--or a nearby terminal. The GPS is often subject to voltage drop because of corrosion and other variables. The monitor mentioned have the advantage that they show current used at any one time, total current consumed, and current in, plus a status of the battery charge--as current in and out--as well as voltage, which is only a rough state of battery "health".
 
Something came up in this discussion that I have often wondered about. Why is it possible to run a 3 stage battery charge controller on inboard engines, but every outboard I know of has the old outdated charger that will not top off the batteries.

Does anyone make one to install over the manufacturer's stock system. Better yet, could one of you retired EE's come up with a design. I, for one, would purchase one.
 
anchorout":3vsumbi5 said:
Something came up in this discussion that I have often wondered about. Why is it possible to run a 3 stage battery charge controller on inboard engines, but every outboard I know of has the old outdated charger that will not top off the batteries.

Does anyone make one to install over the manufacturer's stock system. Better yet, could one of you retired EE's come up with a design. I, for one, would purchase one.
Click to expand...

Yes, you could put a smart charger on any alternator. i have done this on larger boats where I was running a diesel 24/7.

I suspect that first is that most people do not use their boats the way we do, so the demand is not there for the outboards.

The other part is that a "smart" battery charger has the three stages: the Bulk is where most of the outboards are--this is a high voltage--in the 14 to 14.6 (upper limit) volt range. This is the rapid phase of battery charging.

During the Absorption phase the regulator detects voltage and resistance from the battery during charging which determines the battery has reached about 80%* state of charge which maintain a steady voltage, while the amperage declines and brings up the battery charge without overcharging or heating. This protects the battery, but takes time at a lower amperage output.

The Float stage will start in the 85% to to 95% amount of charge, will be in the mid to low 13 volt range (even tapering to high 12 volts in some cases}, as it tops off the final few amps of capacity.

As you can see, this latter takes time, to avoid over charging or damaging the battery. Some of the newer batteries, can take more charging current in shorter times--such as the Li ion batteries--but at this point they are expensive.
 
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