battery question - Gel-cells

[Neverbored]

I'm looking at replacing two 4D Flooded lead acid batteries with two 4D Gel-cells on a Catalina 310. Concerned after reading the alternator on Universal M25 Diesel setups have maximum voltage settings of 14.8 to around 15 volts???? and aren’t adjustable.

Have read Gel-cells shouldn’t be exposed to more than 14.1 to 14.3 volts for any extended recharge period, depending upon manufacturer-specific recommendations. This renders gel-cells completely unusable on any boat with a standard alternator arrangement that utilizes an internal voltage regulator whose setup has a maximum voltage setting of 14.8 to around 15 volts and aren’t adjustable. Will the alternator setup on the Universal M25 Diesel alternator slowly destroy the gel-cell batteries every minute the engine is running.

Fact or myth?

 

[Stu Jackson]

Myth -- that is until you read the output voltage on the alternator at the battery bank on YOUR boat.

M25 engines came with a Motorola (or sometimes Prestolite) 51 or 55 A alternator with internal regulation. In the days before I installed a higher output alternator and MC-612 external regulator and a Link 2000 to measure it all, I recall seeing 14.2 V from our alternator measured at our batteries (we also had an Automac voltage regulator).

Given the choices you describe, I suggest you reconsider. 4D batteries are backbreakers, regardless of wet or gel. I consider them a personal hazard. Why not consider golf carts or standard wet cells? Maine Sail, back when he had his 310, IIRC, put four golf carts in the standard battery box. I'm sure someone can point you to that link here on the C310 section of this board.

Most alternators, whether dumb internally regulated or externally regulated will, by default, charge at wet cell parameters, and you are correct that they are too high for gels. If you have a Leece Neville adjustable internal regulator, you can change the voltage. The OEM Motorolas can't unless you perhaps bring it to an automotive shop. Any external regulator will allow you to change the voltage.

You didn't mention it, but what shorepower charger do you have? Can its volatge be modified, too.

In general, the additional cost for gel or AGM is rarely worth it compared to the bang-for-the-bucks for wet cells. Unless you have batteries in an impossible place to get to, which IIRC isn't the case on your boat.

Good luck.

 

[Maine Sail]

I'm looking at replacing two 4D Flooded lead acid batteries with two 4D Gel-cells on a Catalina 310. Concerned after reading the alternator on Universal M25 Diesel setups have maximum voltage settings of 14.8 to around 15 volts???? and aren’t adjustable.

Have read Gel-cells shouldn’t be exposed to more than 14.1 to 14.3 volts for any extended recharge period, depending upon manufacturer-specific recommendations. This renders gel-cells completely unusable on any boat with a standard alternator arrangement that utilizes an internal voltage regulator whose setup has a maximum voltage setting of 14.8 to around 15 volts and aren’t adjustable. Will the alternator setup on the Universal M25 Diesel alternator slowly destroy the gel-cell batteries every minute the engine is running.

Fact or myth?

It is a fact that over charging gel cells will ruin them. Over charging causes air bubbles to form in the Jello like electrolyte. These bubbles are permanent and once they form the battery begins to degrade. The gel is thick enough that bubbles will not dissipate hence the below gassing absorption charging voltages.. Most gels can't be charged at more than 14.1V. Best to check with the specific manufacturer because some are lower than 14.1V and some as high as 14.2-14.3V...

I am currently working an a boat with close to $2000.00 in TPPL AGM batteries and over $2000.00 in charging system hardware and electronics to treat them right....

If you are going to spend the money on either AGM or GEL technology then an external regulator should be included in the upgrade. gel's can last the longest of any technology but ONLY if charged properly. Gel and AGM should also be charged temp compensated so a temp sensor in addition to the regulator is a very good idea.

On another note I would suggest looking at a case size other than 4D. Manufacturers use them because they are cheaper to install, in bulk and require less labor and cables to install. Beyond that a 4D or 8D has no benefit and only the possibility for a slipped disc and the end of a sailing career. Also most 4D batteries are not true deep cycle batteries but rather "dual purpose"....

I sold my 310 before the 4D's died so never got to upgrade them, but I did parallel them into a single house bank and added a starting battery. It all fit in the factory location.

 

[Neverbored]

Gel cell to 6V Trojans

Thanks Stu & Maine Sail......I decided to go with your suggestion of the four 6V Trojan T-105's. I also replaced the charger with a Charles Marine 30 amp 2000 series. Interesting in my conversation with the battery store.......I asked how long a 55 amp alternator would take to charge the four 6V Trojans depleted to 50% and he said the 55 amp alternator wasn't strong enough to charge the batteries.
Frustrating getting the info you need on this stuff some times.
I definitely appreciate the insight given by you two!