Hey Mike, not to hyjack this thread but, what do you mean a tender doesn't charge up a battery? Explain that. I'm surprised no one else is asking that?

 

Frequently Asked Questions

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How can the Battery Tender Plus battery charger that is rated at 1.25 amperes recharge a battery as fast as another charger that is rated at 3 amperes?


To recharge a battery, it is necessary to replace the charge that the battery delivered during the last time that it was used. The dimensions or units describing electrical charge are the Coulomb or, more conveniently in the context of battery charging, the Amp-Hour. The abbreviation for amp hour is Ah. A battery charger delivers charge (amp-hours) to the battery by using an electrical current (Amps) at its output over a period of time (Hours). The numerical product of the electrical current and time period is the amount of charge delivered. This is true in a general sense for any charger.

What is not obvious is that for the calculation of charge returned to be valid is that the electrical current at the output of the battery charger must be constant during the period of the calculation. This, and the amplitude of the charge current are the critical features of a battery charger that determine how fast it will recharge a battery.

Because of the many different ways that a battery charger can be constructed and electronically controlled, there are many cases where one charger can have a higher numerical charge current rating and yet not charge a battery as fast as some other charger with a lower current rating. This is unfortunate for the consumer because there is really no way to tell based on industry standards because the standards define construction and fault protection methods to ensure safety. Those standards do not define a framework that limits how a battery charger’s numerical charge current rating is determined. This is not unlike some of the confusion that exists when attempting to compare a battery’s performance based on its ratings, although the Battery Council International (BCI) clearly defines the tests that must be performed on a battery for it to be rated at a specific number of cranking amps. No such governing body exists to define a similar testing process to control how manufacturers rate the charge current output of a battery charger.

The confusion with batteries is application specific. For example, ’How long will a 950 Amp battery run the trolling motor in my bass boat?’ The 950-amp rating tells the consumer how many amps the battery will deliver for 30 seconds, when starting an engine, at a specific temperature before the battery terminal voltage drops to 7.2 volts. The 950-amp rating says absolutely nothing about the capacity of the battery, which is what you really need to know to estimate the answer to the trolling motor question. However, the BCI does define a different rating that is more appropriate for that application. That rating is the “Reserve Capacity”. The reserve capacity is the number of minutes that the battery will deliver 25 amps while the battery terminal voltage remains above 7.2 volts.

With battery chargers the electrical current rating alone cannot ensure an accurate estimate of recharge time. Only by looking at the charge current time profiles of two chargers connected to the same size battery, in the same state of charge, can one accurately compare recharge time.

Deltran’s claim that the 1.25 amp Battery Tender Plus battery charger will charge a battery in the same amount of time as a typical 3 amp charger is based on the fact that the Battery Tender Plus charge current is very nearly constant during the bulk charge period, while a typical 3 amp charger, configured like so many chargers on the market, is not.

 

that's a mouthful and my eyes glazed over

a "tender" or trickle charger will keep a charged battery charged, but does not have the capacity to charge a dis-charged battery.

battery chargers do that well and the current of the charger needs be matched to the battery

mike

 

bad cell in batt. if its original, replace it.

 

Hook a meter to the + and - on the battery. , should read at least 12 volts, if not charge before replacing the battery. If battery voltage is good try cranking it with the meter hooked up. If you drop 2 or more volts it's probably the battery. You can also peck on the starter while trying to crank and see if the starter rolls over. If so it is probably the starter windings shorting pulling down the battery.

 

Mine did that couple years ago and turned out be the ground wire had corrosion due to washing it.