It seems like there are tons of information on the internet about these new technology batteries as they work their way into the golf cart market, but what does it all boil down to, right now? Let’s take a look and see if we can figure things out a bit.
According to my research, it seems as though the lithium-ion batteries first appeared in the American marketplace in camcorders, in 1991. So, they have been around for quite a while, but are just now finding their way into golf carts. The technology has gone through some major changes through the years, due to the fact that the lithium-ion batteries tend to be quite unstable, and require some carefully designed “extra circuitry” to make them safe. The basic problem is that the materials contained in a lithium-ion battery are highly flammable and demonstrate instability at elevated temperatures. In order to regulate the temperature, the amount of voltage and current being used to discharge and re-charge the batteries must be monitored and regulated at all times, and if certain parameters are exceeded, the battery needs to be “shut down” for its own protection and the safety of others. The latest control circuitry developed to “do the job” is called a BMS, which is short for Battery Management System.
Each golf cart lithium-ion battery that you buy has its own BMS, which consists of a circuit board loaded with “chips” designed to do the job. Each battery is composed of many internal cells of around 3.6 volt each. They are arranged in parallel and series configurations (within the battery’s case) in order to meet the voltage and current ratings of the battery as a whole. The battery might end up as a 6-volt battery, or an 8-volt battery, or a 12-volt battery, or even a 36- volt or 48- volt battery, depending on the type of cart that it is intended to be used in. It is the primary job of the BMS to keep an eye on the currents, voltages, and heat and manipulate things within the battery so that it performs at its best level and doesn’t exceed any of the limits that we mentioned earlier. Interestingly enough, it actually does this monitoring and adjusting of current and voltage levels at the CELL level. This prevents the cells from being over-charged or under-charged and even shuts the battery down, if necessary to keep things from going terribly wrong (like catching on fire or blowing up). When the battery gets discharged to the point that it can’t be safely used anymore, until it is re-charged, the BMS shuts the battery down. With conventional lead-acid batteries, as the cart gets discharged to a lower level than the system needs to operate properly, you feel the cart start to slow down. Not so, with lithium-ion batteries, they just shut off all together. Most lithium battery conversion kits include a charge meter that the driver can observe to determine when to get the cart on a charger in plenty of time, so as not to get caught out with a “shut down” battery pack. We could spend a bunch of time on the inner workings of the lithium-ion cells and the BMS, but that isn’t the purpose of this post.
Why would you want to replace your lead-acid batteries with lithium-ion batteries in the first place? There are several advantages so let’s make some comparisons.
A typical configuration for a conventional 36-volt golf cart would be for it to have 6 Trojan T-105, 6-volt batteries connected in series for a total of 36 volts. Each battery has a current rating of somewhere around 225 ampere hours (Ah). A typical configuration for a set of lithium-ion would be to have just 2, 36 volt batteries with a current rating of 36 Ah each, connected in parallel for a combined current rating of 72 Ah, to accomplish the same 36 volt supply. Batteries connected in series “add up” as far as voltage goes, but since all of the current goes through all of the batteries in series, the current available is the same as for just 1 of the batteries. As a matter of fact, the current is actually limited to that of the weakest battery in the pack. So, if you have one battery that can only supply half as much current as it should, your whole pack is held to half of its normal supply of current. With batteries connected in parallel, the voltage available from the battery pack is the same as each of the individual batteries (in our case 36 volts) but the current that is made available equals that of the 2 batteries added together. Therefore, to increase the current available and therefore the distance that the cart can travel, more batteries can be placed in the parallel configuration. So, instead of having just 2 batteries in parallel, as in our example, if you wanted to go farther you could just add another 36-volt battery to the configuration. There are some “special” considerations, however, that need to be observed in adding additional lithium-ion batteries that we will get to later, but for now, just remember that adding batteries in series adds to the voltage, while adding batteries in parallel adds to the available current.
The first consideration in our comparison between 6 conventional (lead acid) batteries in series and our new set of (2) lithium batteries is that of weight.
Conventional lead acid 6-volt golf cart batteries weigh in at around 62 lbs., for a total of 372 lbs. The lithium-ion batteries come in at about one fourth of that, or about 15 lbs. each, but the installation usually only requires 2 or 3 batteries. That may not seem like a big deal, but if you are the one that has to do the lifting when replacing them, it is a BIG deal. This also makes the cart much lighter, so it performs better.
The next consideration is “range” How far can the golf cart go, before it must be re-charged. The Trojan T105’s were designed so that a set of them can make about 3 trips around an 18 hole golf course before requiring charged. The usual distance a cart is driven around a typical golf course is about 6 miles (give or take a little, depending on how much time you spend out in the woods looking for your ball), so we’ll say that means about 18 miles for 3 rounds. Now you would think that with 225 Ah, it could make it farther than that, but not all of the Ah’s are usable, without doing harm to the batteries. That makes the 225 Ah not as much as it first appears to be. Most lead acid battery manufacturers recommend only discharging their batteries to about 50% to 80% of their maximum state of charge (SOC) before recharging them. The range of our 2 new lithium-ion batteries in parallel is advertised by their manufacturer to be 15 to 20 miles (depending on terrain, etc.). The reason that they can make it that far with only less than half the current rating, is that almost ALL of their energy can be used before they need re-charging, without doing any damage to the batteries. Remember that BMS? That is what it is good at. And if you needed some additional range, you could just add another battery to the parallel combination. The manufacturer boasts that adding a third battery would extend the range to between 20 and 25 miles. WOW! That is great.
The next consideration is that of maintenance. With the conventional batteries, you MUST constantly check and maintain the level of the electrolyte (a messy job to say the least). With the lithium-ion batteries there is NO maintenance to be done.
Here are some other benefits to having the lithium-ion batteries installed:
No corrosion to eat up battery boxes or cables. No more of that “white stuff” on your driveway.
Much faster re-charge time. The manufacturers of Lithium-ion batteries boast of a re-charge time of up to 5 times faster than lead acid batteries.
They “self-discharge” at a much slower rate. That means that when they are left sitting for a long time unattended, they maintain their charge much better. This is great for those who leave their cart at a second home for a season at a time.
Another advantage is that the lithium-ion batteries will out last the lead acid batteries by an incredible length of time. Most of the 2 battery lithium-ion kits come with a warranty of between 8 to 11 years. The thing that you need to be aware of though, is that to properly charge the new batteries, you will need a special charger, designed to do just that, in an efficient manner. Some of the kits come with the charger included in the “deal”, but some don’t, and are made available at an extra charge of around $250.
There is, however, one HUGE disadvantage to buying the lithium-ion batteries. Their COST. Right now, the price for a typical 2 battery kit to convert from lead acid is about $2000. Ouch! But, considering how much longer they will last, and all of the other advantages, I think they are certainly the wave of the future.
Earlier, I mentioned adding additional batteries into the parallel configuration, to increase the available current and therefore the range of the cart. They can even be connected in series in order to increase the voltage of the battery pack, as in connecting 3, 12-volt batteries in series to provide 36 volts. But because of the function of the BMS contained by each battery, it is VERY important that any batteries added to the pack have precisely the same characteristics as the existing batteries. If the match isn’t “almost perfect”, the BMSs on each of the batteries can react with each other in such a way as to not allow for an absolutely perfect charge or discharge. Some lithium-ion battery manufacturers acknowledge this and even advertise that the voltage and current ratings may only be 90% of what they would be with a single battery installation. The general theory is that “the fewer the number of batteries in parallel (or even in series), the better”. The less BMSs there are trying to protect their “flocks” of cells, the less issues with interaction between the BMSs. Added batteries MUST be of the same battery chemistry and batteries of different ages, or even from different manufacturers, should NEVER be mixed.
I have NOT had the opportunity to do a lead acid to lithium-ion conversion yet. Ironically enough however, my old Hyundai golf cart has just started suffering from old lead acid battery symptoms. Now I’ve got to make a decision. To replace the lead acid batteries for about $750 (plus labor), or to go ahead and make the shift to lithium-ion for about $2000 (plus labor). In this case, the value of the old cart certainly doesn’t justify putting $2000 in it, but with all of the additional benefits and longevity of life that the lithium-ion batteries would offer, I am certainly tempted to “bite the bullet” and go ahead and make the conversion. If something else “croaks” on the cart, rendering it useless, I could move the new batteries to a replacement cart, as long as I move them together and don’t try to “mix” them with anything else.
Ron Staley has published the following books, and you can get more information about them by just clicking on each title below:
Electric Golf Cart Repair 101 (and a half)
Techniques, Tips, Tools and Tales
Gas Golf Cart Repair 101 (and a half)
Techniques, Tips, Tools and Tales
4-Stroke Golf Cart Engines Explored
What Makes Them Tick
By an old Slot Machine Mechanic